• Preheat oven to 350°F (175°C). Combine graham cracker crumbs, sugar, and melted butter, then press into a 9-inch pie pan. Bake for 10 minutes and let it cool completely.
• In a saucepan, combine blueberries, sugar, cornstarch, and water. Cook over medium heat, stirring, until thickened and berries burst, about 5 minutes. Cool slightly and spread over the cooled crust.
• Whisk together sweetened condensed milk, lemon juice, lemon zest, and egg yolks. Pour this mixture over the blueberry layer and bake for 15 minutes until set. Cool to room temperature, then refrigerate for at least 2 hours.
• Whip heavy cream, powdered sugar, and vanilla extract until soft peaks form. Spread the whipped cream over the chilled lemon layer just before serving.

Notes

• Use fresh lemon juice for the best flavor and avoid overbaking the lemon layer. Chill bowls and beaters before whipping cream for faster results. Wipe the knife between cuts for cleaner slices. Can be prepared a day ahead, adding whipped topping just before serving. If using frozen blueberries, thaw and drain them first.
• Serve with vanilla ice cream, lemon sorbet, herbal iced tea, sparkling lemonade, or chilled white wine. For variations, use gluten-free graham crackers, substitute blueberries with other berries, or add lemon zest to the whipped topping.